Resilient sheet floor coverings, such as vinyl floor coverings are widely used in residential construction. A vinyl floor covering, as used in Europe, is typically composed of a number of layers including a wear layer, a print/foam layer, a glass mat layer and a backing layer. The wear layer is typically polyurethane and provides the hard, abrasion-resistant surface required for good durability. The print/foam layer carries the decorative print and is chemically foamed and embossed. The glass fiber layer is typically a mat in the range of 35 g/m.sup.2 to 60 g/m.sup.2 produced with a suitable binder material. The backing layer is vinyl film typically having the same mass as the print/foam layer. The backing layer may be solid or foamed and completely encapsulates the glass mat.
Unlike the floor coverings produced with felt or paper carriers, the glass mat provides a dimensionally-stable substrate for coating and printing operations during production of the floor covering. Felt backed vinyl floor coverings are often adhered to the floor surface. The use of the reinforcing glass mat as an interlayer yields a floor covering that resists curling, making the floor covering suitable for loose-lay installations. In addition, the interlayer construction is very flexible, making do-it-yourself installation readily possible.
Vinyl floor coverings containing such an interlayer of glass fiber mat have been widely used in Europe. However, the use of an all glass fiber mat as a reinforcing layer in vinyl floor coverings has not been widely accepted in this country, because of the difference in building construction techniques. Concrete subfloors are prevalent in Europe while wood subfloor systems are more widely employed in the United States. The relative dimensional stability of such glass fiber reinforced vinyl floor coverings is desirable when installed over concrete, but may cause problems when installed over a wood subfloor. Wood subfloors exhibit relatively large dimensional changes in response to temperature and humidity changes. In winter time, wood subfloors tend to dry out, shrinking the wood by as much as 0.5%. Unless the floor covering is able to compress (i.e., shrink) along with this dimensional change in the subfloor, the floor covering may respond by buckling.
Prior glass fiber mats used to reinforce vinyl floor coverings have typically been very stiff and have exhibited a high resistance to planar compressive movement. A typical reinforcing mat used as an interlayer in vinyl floor coverings is made with glass textile fibers having a diameter in the range from 9 to 11 microns and a length of 6 mm. These fibers are typically held together by a rigid polymeric binder, such as a urea-formaldehyde resin or poly(vinyl alcohol). The high compressive stiffness of these glass reinforcing mats is not substantially altered during the manufacturing of the floor covering.
U.S. Pat. No. 4,849,281 discloses one potential solution to the problem of the high compressive stiffness exhibited by such glass fiber reinforcing layers. The glass fiber mat disclosed in this patent is a blend of mostly glass wool fibers with a balance of glass textile fibers. These glass fibers are bonded with a crosslinked styrene-butadiene elastomeric binder that is softened by the plasticizers in the vinyl coatings. The combination of mostly short, friable, glass wool fibers and the rubbery binder permit a substantial amount of compressive movement in the corresponding floor covering. This compressibility, in turn, may reduce the chance of buckling when the floor covering is installed over a wood subfloor.
Even though the glass fiber mat disclosed in U.S. Pat. No. 4,849,281 provides one potential solution to the problem of high compressive stiffness, there is a continuing need for more commercially acceptable fiber mats capable of providing resilient sheet floor coverings with even better planar compressibility.